The present invention relates to material removing arrangements.
More particularly, the present invention concerns an arrangement for chipping a workpiece of wood.
Such arrangements are well known in the prior art and usually include a support component for an elongated workpiece and a tool component rotatable about an axis and having a circumferential cutting face and axial end faces. At least one of these components, i.e., the support component and/or the tool component, is movable relative to the other component during the working process. The tool component is mounted, at both end faces thereof, for rotation about this axis. The workpiece is displaced intermittently in a direction substantially transverse to the movement of one of the above-mentioned components during the working process. Thus, the workpiece is displaced in this direction so that a portion of the workpiece, to be removed is equal to or smaller than the axial length of the tool. Thereafter the working process starts and the above-mentioned portion of the workpiece may be removed.
Such an arrangement is disclosed, for example, in German Auslegungsschrift No. 1156965. The cylindrical tool is fixedly mounted on a shaft whose bearing supports the tool from both end faces thereof. The bearing element which faces the workpiece to be treated is located in the interior of the tool so that when, during the working process, the tool engages the workpiece, the workpiece passes the bearing support without touching it. However, the advantage of the fact that the tool is mounted at both end faces thereof can be derived only when the height of the workpiece to be cut into chips is much too small as compared with the outer diameter of the tool. Thus, the advantage of supporting the tool from both end faces thereof, which permits to correspondingly increase the axial length of the tool and which in its turn renders it possible to increase the working capacity of such an arrangement by increasing the length of the portion to be removed from the workpiece, is substantially negatively offset by the necessity to keep the height of workpiece to cut into chips significantly small.
Another disadvantage of the known arrangement resides in relatively high and very inconvenient axial loads on the bearing of the shaft supporting the tool. During the working process, the front end face of the workpiece (i.e., the end face which has been already treated) frictionally engages the adjacent end face of the tool and exerts onto the latter axial percussive loads which considerably increase for example during disintegration of the wood structure. These axial loads are transmitted from the tool via the shaft onto the bearing and further onto the other parts of the arrangement. It goes without saying that such loads considerably reduce the service life of the bearing.
Moreover, the frictional engagement between the front end face of the workpiece and the adjacent end face of the tool which rotates with a rather high speed results in considerable vibrations of the workpiece which, obviously, negatively affect the working process.
The above-mentioned disadvantages of the arrangement, where the tool is supported from both end faces thereof, are widely known. There have been attempts to improve the tool having a cantilever support. Usually, these attempts were limited to reducing the inherent shortcomings of the cantilever support of the tool to the most convenient extent. Such as arrangement is disclosed in German utility model DGBM No. 76 19632. The tool is fixedly mounted on a sleeve which is supported by two bearings which are located on a rigid shaft which is rigidly mounted on a support. However, even in this case the useful axial length of the tool has to be kept substantially small since, otherwise, the bending moment exerted onto the tool during the working process can be extremely large. The tool may become deflected as a result of contact with the workpiece, e.g., a piece of wood installed on a carrier, so that, the working (i.e., cutting) relationship and an angle between the tool and the direction of the elongation of the wood fibers may be negatively changed. This fact may lead to substantial reducing of the quality of chipping, for example, especially when the workpiece is a weak long wood piece and as a result of dust accumulation on the tool.
Moreover, the oscillations of the tool mounted on the cantilever may lead to contact between the tool and the counter tool. As a result of such a contact the tool may become suddenly dull, and therefore, it has to be replaced quite often which is, obviously, undesirable for a number of reasons including expenses, time consumption, etc. and, in an extreme situation, more serious damage can be done to the tool itself, or to the counter tool.